Aristotle’s physics weren’t the only aspect of his scientific ideas to make it into Catholic church; his thoughts on biology were also integrated into the Thomist system, and nowhere can this influence be better seen than in the Catholic response to so-called “life issues.”
Since Aristotle was trained as a doctor and appears to have engaged in dissection of zoological specimens, his biological observations have aged better than his conclusions in the astronomical and physical sciences; he was the first to note that whales and dolphins were distinct from fish, for example, and also discovered that sharks give birth to live young. However, without access to a microscope, recourse to the scientific method, or a communities of like-minded peers to challenge him, Aristotle could only go so far with his investigations.
The basis of the Catholic opposition to abortion, contraception, IVF, and masturbation stems from Aristotle’s belief in the existence of homunculus, or “little man.” He thought that sperm consisted of a “little man” that needed to be implanted into the womb, where it would eventually grow into a baby — a male baby, to be precise. Since Aristotle assumed that maleness was the default for the human species, the birth of a female baby was indicative that something had gone wrong with the “little man” and the pregnancy, as women were regarded as “misbegotten men.” Aristotle also believed that men contributed all the material needed to produce a baby through their “little man” and that women merely incubated the resulting fetus until it was ready to be born. This is why children were considered to be the property of their fathers in the classical world, since it was believed that their mothers could not claim a biological link with them. To be fair, the full role of women in the reproductive process was not discovered until the nineteenth century, but as we will see, Aristotle’s erroneous conclusions on the matter continue to carry weight into the present day.
As I mentioned before, when Thomas Aquinas integrated Aristotelian science into his theological worldview, he was acting under the assumption that Aristotle was describing the universe as it actually was. Among the ideas that Aquinas accepted was Aristotle’s concept of the homunculus. When placed within the Catholic Thomistic framework, the homunculus took on a new moral significance. Concerned with the dignity of “the little man,” Aquinas concluded that male masturbation was worse than rape, since the latter was at least “natural” and could lead to pregnancy, whereas the former wasted the life-giving potential of the homunculus (does this mean female masturbation is licit, since there is no homunculus or semen to waste?).
While the existence of homunculus was thoroughly debunked some time ago, this notion still lurks in the background of the Catholic response to “life issues.” I suspect that the lingering belief in the homunculus as a fully formed “little man” that just needs a womb in which to incubate for nine months could explain why conservotrad Catholics assert that newly fertilized eggs, zygotes, and non-viable fetuses to be “babies” that have the same moral status as a toddler, despite the considerable amount of evidence to the contrary. Because of the limitations of technology in classical antiquity, I’m willing to give Aristotle a pass on his confusion surrounding the finer points of the human reproductive process. I’m not so forgiving of modern individuals who use discredited Aristotelian science to further their religious agendas.